The role of supinator in the pathogenesis of chronic lateral elbow pain: a biomechanical study.

The relative contributions of the forearm extensors to the tensile force at the lateral epicondyle were examined by implanting a force transducer in the common extensor tendon of four soft fixed cadaver elbows and sequentially stretching each muscle arising from the lateral epicondye. Extensor carpi radialis brevis and extensor digitorum communis produced the largest increases while the superficial head of supinator produced a moderate increase in tensile force in the common extensor tendon. Extensor carpi radialis longus and extensor carpi ulnaris had no significant effect. Radial tunnel pressure was measured using a balloon catheter in a separate study of five cadaver elbows. Radial tunnel pressure increased on moving the wrist from neutral to a flexion-pronation position. This positional rise in pressure was reduced by supinator musculotendinous lengthening (77%) while lengthening of the extensor carpi radialis brevis and extensor digitorum communis had no effect. This study demonstrates a biomechanical basis for the superficial head of supinator in the aetiology of both lateral epicondylitis and radial tunnel syndrome.